Agreed. The sense of focus is lost in Tim's. While it's probably more accurate, a key part of art is selective distortion, guiding the viewer to focus on certain things.

I also disagree with his assertion that Vermeer is photorealistic. Very realistic, true, but not more than other Dutch masters, and there are many contemporary artists whose paintings and drawings truly are indistinguishable from photographs.

Is that "Tim's" feet in the reflection in the mirror?

I first saw a piece about this painting a long time ago, possible an Open University / BBC collaboration - it was concerned with the room being the wrong length to allow for the optical method people thought was used, or some such, I don't recall too well.

Other (?) speculation has been on here not too long ago.

It's the corner of the carpet on the floor tile - the one farthest from us, not the one in the foreground of the painting. I work in film and one thing cinematographers love doing is shooting into mirrors, so I've gotten used to checking them for continuity purposes :)

As for the dimensions of the room, being 'wrong', that may be deliberate. Again in film props and furniture are adjusted out of their natural position surprisingly often, in pursuit of aesthetic harmony. If you analyzed an interior scene that had been shot from multiple angles in hopes of mapping the room's contents accurately, you'd be disappointed to discover that many things had changed position by ~10% of their own size from shot to shot. Part of the craft is the ability to look at the image on a tiny monitor and be able to identify whatever it is that is distracting your eye from where you're supposed to be looking, like a table which looks fine in one shot but feels too small following a change in the focal length of the camera lens for a different shot. Solution - move the table towards the lens a bit.

Don't even get me started on lighting and related tricks, which can further mess up your spatial intuition. For example, a very common and cheap effect is to make a room feel bigger by painting adjacent walls slightly different shades of the same color. Lots of these techniques are stolen from painting, where the deliberate falsification of perspective has long been used for both aesthetic and semantic effect. Check out this especially famous example: http://en.wikipedia.org/wiki/The_Ambassadors_(Holbein)

The better question is what is the mirror reflecting in the Vermeer?

Yup, looks like his feet to me, as well as the feet of his desk. He seems to facing sideways (to the left)

The woman is facing the wrong way in Vermeer's, isn't she?

No, she's facing the right way - it's a music lesson, so she's facing the instrument which she's playing. But she's looking slightly towards the (I assume) teacher, as if asking "Am I doing this right?". On Tim's version, she has abandoned the instrument completely and is just talking to the gentleman, who is also much more engaged with her judging by the body postrue - I'd say even there's something else than music lesson going on in that version :) So these paintings, while being similar, actually depict two quite different situations.

She is facing the right way but her reflection in the mirror isn't.

It looks to me that their heads are pointing in about the same direction (looking at the man) but in Vermeer's she is turning her head (her body is facing another direction)